WikiLeaks, which began releasing 251,287 US diplomatic cables in November, added it had reason to believe Facebook and Google had also received court orders requesting details on users.
"Today [Saturday], the existence of a secret US government grand jury espionage investigation into Wikileaks was confirmed for the first time as a subpoena was brought into the public domain," WikiLeaks said.
WikiLeaks said legal action taken by the micro-blogging website Twitter "revealed that the US State Department has requested the private messages, contact information, IP addresses, and personal details of website founder Julian Assange and three other individuals associated with WikiLeaks, in addition to WikiLeaks' own account, which has 634,071 followers."
It did not name the three other people, but Icelandic lawmaker Birgitta Jonsdottir said on her Twitter feed on US authorities had asked Twitter to submit her account details and personal information.
"Just got this: Twitter has received legal process requesting information regarding your Twitter account in [relation to wikileaks]," the media freedom champion posted overnight.
Ms Jonsdottir - a close associate of WikiLeaks who in September suggested Mr Assange step aside as the site's spokesperson because of rape allegations against him - said she discussed the request with Iceland's justice minister.
"He is looking into the case of demands of DoJ [department of justice] wanting my twitter details," she posted.
She explained she had 10 days to stop the legal process and stressed the US Department of Justice, not Twitter, was to blame.
WikiLeaks said it was "opposing the subpoena order and is currently taking action to instruct US lawyers."
It urged Twitter to protect its users' private information and stressed that other than Mr Assange, the three people whose accounts had been subpoenaed had never worked for the site.
Mr Assange, the 39-year-old Australian who is the public face of WikiLeaks, is currently on bail in Britain facing extradition proceedings to Sweden on charges of sexual assault.
Assange has now hired a "public relations firm", apparently in a last ditch
desperate attempt to influence the British Court not to deport him, on his next
court date of Tuesday January 11, 2010.
Assange is the author of his own dysfunctional personality that apparently leaves behind it a trail of destroyed relationships which include his closest associates who now refuse to work with him.
Assange can fool some people some of the time but he can't fool most people most of the time.
The Three Swedish women simply wanted to know if he had an STD, such as HIV and two days before Assange agreed to meet with police he chose to flee the country.
The women did not seek rape charges but its pretty clear that the police acted appropriately.
Assange was given consent to protected sex only, he later without their consent had unprotected sex. No wonder these ladies are worried.
Assange admits to being an 87% slut, he wants to create children (read have unprotected sex), he also likes the occasional criminal conspiracy.
That's damning evidence right out of his own mouth that he used to, wait for it, "attract women".